1. Field of the Invention
The invention generally relates to a membrane welding apparatus including a visual seam marker. More particularly, the invention relates to a membrane welding apparatus including a visual seam marker for applying an indicia on the upper surface of overlapping thermoplastic and composite type thermoset membranes when the overlapping membranes have been subjected to a sufficiently high temperature to achieve a proper seal between them.
2. Description of the Related Art
Within the last decade, thermoplastic roofing membranes have become significant products in the commercial and industrial marketplace. They provide good service life on flat and low slope roofs while representing a cost effective alternative to built up roofs and other previously available roofing systems. Roofing membrane products are typically manufactured as elongate sheet goods having a width of 3 feet (0.9 meters) or greater which are provided in rolls. The membrane is unrolled on a roof with edge adjacent portions of the membranes overlapped on the roof surface. The overlapped regions are then sealed together.
In order to achieve their service and cost saving potential, these roofing membranes must be continuously and tightly sealed along these overlapping regions. Typically, the overlapping regions are sealed by heating the adjacent surfaces of the overlapping membranes and then pressing the heated surfaces together, merging the material of the membranes and providing a strong seal. The integrity of the seal and thus of the overall roof depends upon appropriate and sufficient heat application to achieve melting of the membrane material and a positive, continuous seal between the overlapping membranes.
A roof membrane welding apparatus for forming a weld is described in U.S. Pat. No. 4,834,828, incorporated herein by reference. The roof membrane welding apparatus includes a nozzle having an outlet of a fixed width for applying heat and producing a weld to the membranes and a single weld wheel located in front of the nozzle to press the two membranes together after the welds have been produced.
The industry has maintained that the roofing contractor has to control and verify the quality of his welding skill by destructive seam analysis and seam probing. The present invention will reduce and or eliminate the time consuming xe2x80x9cseam probingxe2x80x9d once destructive seam analysis criteria have been fulfilled.
In all hot air welding operations of any and all heat welded materials, the operator must select the proper speed, temperature and pressure to effect a weld between the various gauges and colors of membrane types. He must be knowledgeable of the factors that will vary the ultimate strength of his constructed bond. The conditions (weather, housekeeping practices) of the job site will also effect the resultant strength of the final weld.
Destructive Seam Analysis tests require the following, at the beginning of each day""s seam welding, the operator responsible for seam integrity must perform the following destructive seam analysis by cutting out a 2.5 cm by 15.2 cm (1 inchxc3x976 inch) cross section of the seam and perform a peel of the seam sample. This should result in the destruction of either the bottom surface of the top membrane or the top surface of the bottom membrane (ability to see the fabric reinforcement of the membrane). There should be separation of the weld down to the scrim or fabric reinforcement or membrane(s) destruction outside the welded area.
This type of testing should be performed every time there is an interruption in the welding process (i.e. power failure, welder shut down, job site condition changes, etc.)
To limit the possibility of blisters in the seam area, never unwrap the roofing membrane rolls until they are to be installed and have the proper time to relax or come to equilibrium with atmospheric or climatic conditions.
The operator must establish hot air welding conditions for all seams constructed daily. Do not expose edges of the unwelded seams to prolonged moisture.
The second, more time consuming seam verification process is SEAM Probing. Probing is a physical inspection of the hot air welded area by using a suitable blunt object (cotter-key puller with the point filed down or #2 Phillips screwdriver with its point filed down) along the length of the weld. Pressure is applied to the raised edge of the weld. A poorly constructed weld will open.
All hot air welded seams must be physically probed and this operation is time consuming but mandatory by all thermoplastics or heated welded membranes system.
One approach to ensuring a membrane-to-membrane seal is the intentional excess application of heat. While this may achieve a seal, it is generally slow as the application of larger quantities, i.e., excess, heat takes longer than the application of the appropriate amount of heat. More importantly, however, excess heat application may result in damage to the roofing membranes which will ultimately shorten their service life. Furthermore, such an approach is energy inefficient. Another approach to ensuring seal integrity involves checking, either visually or mechanically and either on a spot or continuous basis, the seal by manually lifting the edge of the upper membrane to determine if it is properly secured to the lower membrane. Obviously, spot checks can miss unexamined unsealed areas and continuous inspection of every seam is time consuming and therefore costly.
The present invention is directed to a method and apparatus for visually verifying the integrity of a weld of overlapping membranes by the proper set-up of the controlling elements (time, temperature and pressure) of a welding apparatus. The present invention utilizes an indicia caused by the weld wheel to indicate that a bond has been achieved between the mating layers of membrane material.
Briefly, according to this invention, there is provided a roof membrane welding apparatus capable of applying a weld to a first membrane and an overlapping second membrane. The apparatus includes a movably supported chassis, a welder attached to the chassis for heating both membranes to at least the vicant softening point to permit welding of the overlapping second membrane to the first membrane, and at least one weld wheel rotatably attached to the chassis and located rearward of the nozzle relative to the direction of movement of the apparatus. The weld wheel assembly includes a marker having an indicia thereon that is transferred to a top surface of the second membrane only where the first membrane and the second membrane have undergone a phase change during heating.
The integrity of the weld formed between overlapping membranes is verified by pressing a marker including an indicia against the top membrane along the area of overlap such that the indicia is transferred to a top surface of the membrane only where the membranes both undergo a phase change during heating.